We completed and reported this year the results of a double-blind placebo controlled study in which recombinant glycoprotein D of herpes simplex virus types 2 glycoproteins D(gD2) and B (gB2) were combined with an MF59 lipid emulsion adjuvant or the adjuvant alone for the prevention of genital herpes. Approximately 550 adults were vaccinated. Subjects were enrolled in multiple centers and are the monogamous seronegative partners of people with proven HSV-2 infection. Infection was documented by seroconversion, by development of typical oral or genital lesions, and by virus culture. This was the largest prospective study of herpes acquisition ever conducted. Upon analysis of the unblinded data it was observed that the vaccine did not prevent acquisition of herpes. Women were significantly more likely than men to acquire HSV-2 infection. Prior HSV-1 infection did not protect subjects from HSV2 infection, but such infections were significantly less often symptomatic. With the failure of this vaccine, we terminated for the duration, our human studies. We have turned instead to exploration of animal model systems and technologies in which we are testing novel DNA-based and live, genetically-engineered vaccines for genital herpes. This has the theoretical advantage of inducing CTL responses. To optimize the responses, we prepared DNA expression cassettes for multiple HSV-2 structure and regulatory genes and lymphocyte co-stimulatory genes. Initial studies in mice using vectors expressing HSV-2 gD have verified that DNA-based vaccines are highly protective against HSV2 infection. The coadministration of vectors for selected HSV regulatory genes did not enhance the activity of gD-expressing vectors. We are now exploring the value of vectors that enhance the copy number of transfected genes in cells, as well as live engineered virus that is deleted for critical genes, rendering the virus avirulent and less able than normal to establish atency or recur.